// Base32 implementation
//
// Copyright 2010 Google Inc.
// Author: Markus Gutschke
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <string.h>

#include "base32.h"

int base32_decode(char const* encoded, char* result, int bufSize)
{
    // Base32 implementation
    // Copyright 2010 Google Inc.
    // Author: Markus Gutschke
    // Licensed under the Apache License, Version 2.0
    int buffer = 0;
    int bitsLeft = 0;
    int count = 0;
    for (const char* ptr = encoded; count < bufSize && *ptr; ++ptr)
    {
        char ch = *ptr;
        if (ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n' || ch == '-')
            continue;
        buffer <<= 5;

        // Deal with commonly mistyped characters
        if (ch == '0')
            ch = 'O';
        else if (ch == '1')
            ch = 'L';
        else if (ch == '8')
            ch = 'B';

        // Look up one base32 digit
        if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))
            ch = (ch & 0x1F) - 1;
        else if (ch >= '2' && ch <= '7')
            ch -= '2' - 26;
        else
            return -1;

        buffer |= ch;
        bitsLeft += 5;
        if (bitsLeft >= 8)
        {
            result[count++] = buffer >> (bitsLeft - 8);
            bitsLeft -= 8;
        }
    }

    if (count < bufSize)
        result[count] = '\000';
    return count;
}
